Just bought a single white bt disc for extended wifi in my garage ( not on ring main, it has its own ) but after trying to connect it I read it needs to be always connected by Etherley, appreciate my fault for not thoroughly reading all forums , question is, if I get a black wifi disc once connected does it need a wired connection ( power supply is understood ) , should I just buy another white wifi disc which I believe doesn't need ethernet once set up or just switch providers
You always need at least two white discs, as one always needs to be connected by Ethernet, to your router.
If you are a BT Broadband Customer with a Smart Hub 2, then the black discs can connect via wireless.
You cannot mix the black and white discs as they are not compatible.
The white disc form their own wireless mesh, but cannot pair with the BT Smart Hub 2.
As for which is best, I have no idea, as I use a totally different system.